Little Mermaid Falls
by colorful-titanpeanut
Summary: Mabel remembers all of her failed romances but there was that one person she never truly got over. Mermando. She yearned to see him and Bill offers her a deal. How will Dipper help clean this mess and help Mabel marry the love of her life? (Mabel x Mermando and Bill x Dipper)
1. Chapter 1

**Mabel POV:**

Mabel sighed as she moved her feet around in the water of the public pool. It held many memories of her and Mermando. He had taken her first kiss and she never had gotten over him, in all honesty. The brunette had also found out that he was being forced to marry some Princess of the sea. How depressing… She wished she could be a mermaid so she can be with him because well… She loved him.

'It's probably another one of your stupid crushes…' She thought to herself and took her feet out of the water, out her sock and shoes on and exited the place, walking into the woods. "Stupid human legs… Stupid Princess that he's being forced to marry…" Mabel humbled to herself and sat at a tree stump. The girl put her face in her hands and suddenly time stopped around her and everything became silent.

It took her a moment to realize it and she lifted her head, surprised to see black and white all around her. "What the…" In the sun, Bill Cipher's eye appeared and his triangular body all came together as he floated down to her. "Shooting Star, Nice to see you!" Mabel yelped and backed away, realizing she was at the edge of the tree stump. "Stay away you Dorito!" She said while pointing at the dream demon. Bill let out his annoying laugh and played with his cane.

"Oh don't worry kid, I just noticed you were having a hard time with some romance~" She looked down with a slight blush on her round cheeks. "S-Shush, it's not going to work anyways!" The floating triangle twirled around her and lit up brighter. "Well we could make a… **_Deal~" _**His voice became strangely low at the word deal and he peeked a look at her, his eye full of mischief.

Mabel was going to say no immediately but something stopped her and she bit her lip. _'Could he…? Wait, I shouldn't even be thinking about this!'_ She thought to herself. "You can have your boring human legs and let the one you love of your life marry some _Princess. _Or you can become a mermaid with beautiful fins and marry the one you love—"The brunette stood up, looking at the figures of her made by the demons blue flames. Bill Cipher floated in front of her, looking at his back hand a bit smugly.

"Go ahead!" He went around her and leaned in close. "Make your choice!" Bill backed away through his blue flames, waving his hand as he turned. "I'm a busy demon, I haven't got all day." In the dream demons flames, Mermando's face appeared. Mabel was surprised and got closer. "It won't cost much…" She adored the Spain looking face almost not hearing Bill. "Just your…" Bill's whole body became red as he surged forward, the image of Mermando dissolving suddenly and a bit violently, his eye wide and dark, his pupil glowing red. **"…VOICE!"**

Mabel gasped and leaned back, her hands in front of her. She tried to make a decision, wanting to see Mermando with all her heart. She hesitated before holding out her hand, turning her head away, her eyes closed tightly. Bill laughed evilly and took her hand, shaking it. "The deal is made!" The dream demon snapped and potions appeared all over. He threw many into his blue flames and if he had a face, he would be grinning like a mad man.

Mabel watched with terror on her face. Bill grabbed her chin and demanded evilly, "Now sing~" She gulped and did as she was told. "Oh-o-o-o-o-o-oh… Their gnashing teeth and criminal tongues conspire against the odds, but they haven't seen the best of us yet~… If you love me let me gooo… If you love me let me gooo~ 'Cause these words are knives that often leave scars, the fear, the fear of falling apart…" Bill laughed evilly and loudly, his form becoming human and Mabel's voice transferred to the dream demons hand and he put it in a yellow locket, shaped as a triangle.

Mabel's eyes widened as she witnessed Bill becoming human and touched her throat as nothing came out when she tried to talk. The human Bill Cipher grinned wildly and put the locket around his neck. His outfit was a yellow tailcoat with black slacks and shoes. His golden hair was short and went to the right, having a tad of an undercut. He also had a dark upside down triangle to cover his right eye and he fixed his black top hat, twirling his cane around with his gloved hands.

"Now then, without your voice, you will have to get Mermando to fall in love with you once again since I erased you from his memories. All he knows is that a girl is out there somewhere and he loves her." The mute girl's arms flailed about. _'Are you serious?! That is so not cool!' _She wanted to say but Bill read her mind and waved her off. "Come on, did you really think it would really be that simple? Good luck!" Bill pointed at her, his magic allowing her legs to come together and form a beautiful pink and purple tail with fins.

With that, the dream demon vanished with her voice, leaving Mabel alone. Since the girl was now a mermaid, she needed water, but the problem was, she was in the middle of a forest. She struggled for water, and flopped around, her eyes wide. _'Help me please…'_ She begged in her mind as she felt her consciousness slipping away from her.


	2. Chapter 2: You're Mine, Dipper Pines

**Dipper POV:**

Dipper was hanging with Wendy when he saw Mabel sigh sadly in the public pool and get out, put her shoes on and walk into the woods. He frowned a bit at the scene and excused himself and followed his twin. He was now seventeen and so was Mabel. _'She must have been thinking of Mermando…' _The brunette thought to himself. Dipper knew that she never forgot him and wouldn't anytime soon.

Mermando and that "Princess" held off the wedding because he denied and was punished of course by his father but now had no other choice to accept the wedding arrangement. Well, according to Mabel who had told him while crying her eyes out so it took him awhile to understand exactly what she was saying. The brunette saw Mabel sigh once again and sit down on a stump, putting her face in her hands. He was going to go comfort her but then everything went black and white, and it in the sun, Bill Cipher's eye appeared. Oh no- "Ma-"

Suddenly he was tied up and had some kind of plant wrapped around his mouth so he couldn't speak. He was Bill Cipher floating down to meet Mabel but gave Dipper and wink first? Wait, could he even wink, he has only one eye- "Shooting Star, nice to see you!" Throughout their whole conversation, Dipper struggled and his eyes went wide as he watched his sister agree to the deal and wanted to scream 'Mabel, don't!' But he couldn't do anything and only helplessly watched. Dipper looked around and spotted the cart nearby. He got his pocket knife and cut himself loose and ran to the cart, finding the keys and drove back to Mabel to see her literally dying with a mermaid tail and fins. "Mabel!" He picked her up and pulled her in, speeding to the Gravity Falls lake as fast as he could.

This whole situation reminded him of the time when they saved Mermando five years ago but this time, it was Mabel, and Mabel was more important than anything in his life. Once at the lake, Dipper threw his sister in the water, panting and hoped to God she wasn't dead. After a moment, Mabel came up, gasping for air, even though she really didn't need to but hell, it fit the dramatic moment. Even though it was cool, Dipper only crossed his arms, glaring slightly at Mabel.

"What the hell, Mabel! Why would you make a deal with _Bill?!_ Of all people! Oh wait, don't answer that because you can't talk!" Mabel looked down ashamed and rubbed her arm, looking as if she wanted to cry. Dipper tried to stay mad, he really did, but he couldn't. He sighed and kneeled next to her on the dock. "I only have one question. Why would you risk this much if you could have just called Mermando over here?" Mabel's eyes widened and she face palmed. Dipper sighed and shook his head.

Bill suddenly spoke in both of their minds. "Oh, and keep in mind, that you have three days to make him fall in love with you, Mabel. You've got until sunset on the third day. Fail to do this, and I will have your soul for dinner! Remember, reality is an illusion, the world is a hologram, buy gold, BYEEE!" And he was gone. Both twins looked at each other wide eyed. "Mabel, cover your ears. SON OF A-" Suddenly a loud horn nearby covered Dipper's loud cursing. Mabel ducked under water and looked around, surprised that she could see everything clearly and wanted to see if she could breathe and inhaled, finding the water was everything she needed.

When she came up again, she noticed she had a shell bra. Awe, how cute- Meanwhile her adoration, Dipper was looking through his journal about how to stop Bill in a deal. It only said, "A deal's a deal, good luck!" He cursed in his mind and closed the book, looking over to Mabel. There was only one thing to do. "Mabel." His sister looked up at him with wide eyes. "You need to go find Mermando and let him fall in love with you again. I'll be counting on you. I will see if I can make Bill not eat your soul."

Mabel nodded and pulled Dipper in for a hug. His eyes widened in surprise but he hugged her back, smiling. "Go get em tiger." He ruffled Mabel's hair and she grinned, diving to the waterfall and swimming up it with fishes all around her. At the top, she waved at her brother and he called out, "Good luck!" He smiled sadly as she swam away but then shook his head and turned, heading to the Mystery Shack and was thinking of an excuse for Mabel to be gone for about three days? Maybe even four days, who knew what was going to happen?

Dipper sighed and walked up to the Shack and Grunkle Stan was counting his money he made for the day inside. He took a breath and walked in. "Hey kid, where's your sister?" Dipper cursed in his mind. "Oh yeah, about that… She asked me to ask you if she could stay over at Grenda's place for three days. They're going to have girl time or whatever they do." Stanford looked as if he was in thought and Dipper added, "She did this face." He did that cute Mabel face his sister did whenever she wanted something, and the strange thing was it looked just the same on Dipper. Their Grunkle chuckled and waved his hand. "Alright, call her and say I said yes." Dipper smiled. "Alright, I'm on it." He went over to the phone and pretended to dial Grenda's phone number and said, "Hey Mabes guess what? Stan said yes, you can stay over there." He put the phone away from his ear before saying, "Okay, Okay, don't made my hearing go out- Have fun." With that he hung up and walked up to the attic, ignoring Stan who had been watching him.

He plopped down onto the bed and opened his journal again. "Okay… There needs to be something here that helps…" Dipper told himself before looking all through the journal. He found nothing that helped and groaned in frustration. How hard could it be to figure this out? Suddenly he heard a knocking on his window and he ignored it before freezing. The window was so high up no one should be able to get to the top. He looked over to the window to see the human looking Bill Cipher upside down, floating. He squeaked in surprise and nearly fell off his bed. Then there was another knock, then another, and another until Dipper was more annoyed than scared now.

He got up and walked over to his window, opening it and whispering. "What are you doing, someone will see you!" He pulled Bill in, looking out the window to see if anyone had seen that and closed the window, then going over and locking the door to his room before turning and looking at the dream demon. "What do you want, Bill?" Bill went upright and tilted his head. "What do you mean I just wanted to see how my little Pine Tree grew up to be~" Dipper's eyebrow twitched and he crossed his arms. "I'm not little!"

"Anymore~" Bill pointed out and floated to him, taking off the others hat and tossing it aside. "Hey!" Bill didn't say anything and pulled the brunette's arms up, seeing the length of them then lifted his leg, leaving Dipper having to balance on one leg. "B-Bill, stop it!" He said quietly, remembering to keep his voice down. Bill looked at him. "Come on, I'm examining you! You're so much taller than last time! Not that it shows when you're near me, I'm taller!" Bill backed him up and made him fall back onto it and he was crawled on top of, the dream demon touching his face to examine it.

Dipper's eyes widened and he blushed a bright red. "W-What the hell are you doing!" Bill covered his mouth and said grinning, "You need to keep in down, don't you?" He gulped, nodding and Bill continued studying him before getting up off of him and taping his chin. "I say you look good for a… How old are you?" He looked up at him and huffed. "I'm seventeen." The dream demon didn't seem to care at all and waved him off. "Yeah, yeah whatever. You look good for a seventeen year old, you've even gotten bigger I might add." The golden haired demon gestured toward his crotch and this only made his blush worsen.

"S-Shut up you pervert!" Dipper sat up and closed his legs. "I'm just saying what's true, Pine Tree." He threw his hands up. "That's not something you should talk about!" The brunette whispered loudly. Bill rolled his eye and looked around his room once again. "Come on, Pine Tree. I'm not like most humans and we need to talk about your sister here." Dipper stared at him for a second, not trusting him at all. "I know we do." Bill looked at the teen and grinned. "There's no way to stop a deal, kid. Unless… You make a deal with me to help with Shooting Star's…~" Dipper glared at him.

"Never in a million years, you stupid triangle guy!" Bill only shrugged and got down to his feet and suddenly got dead serious, walking to Dipper and pushing him against the door roughly and pinned Dipper's hands over his head. Dipper gasped and squirmed, watching the dream demon grin more at his effort. "Listen here, kid. You will stay out of my way and let the deal go as planned. If I cheat, then that's just how I am. What do you expect, I'm a demon. Face it, you can't stop me." He only glared at the golden haired triangle guy before he spat in his face. "Fuck you, Bill." Bill used one hand to wipe the spit off his face and let go of Dipper's wrist and grabbed a fist full of his hair tightly and dragged him to the bed again.

"I think it'd be the other was around, _Dipper."_ His eyes widened in fear and he whimpered, holding onto Bill's wrist. The blonde threw him onto the bed and ripped Dipper's shirt and vest off making him yelp. "B-Bill, stop!" Bill didn't listen and started to rip off his jeans. "W-Wait, Bill please! I'm sorry!" He grabbed Bill's wrists and tried to push them away when there was a banging on the door. "Dipper?! What's wrong?!" The dream demon growled and covered Dipper's mouth, whispering in his ear. "This isn't over, Pine Tree. I'll get you back." With that, he disappeared, leaving the boy panting and wide eyed.

"Dipper?!" Stanford yelled worriedly. Dipper sat up and went to the door, unlocking it and opening it. "Uh, hi… Sorry, Gnomes." Grunkle Stan 'ooh'ed' and nodded. "Gotcha. Be careful will ya?" Dipper only nodded and closed the door again, covering his mouth. That… Was too scary. Sure, he knew Bill could be cruel and evil but that… That sent shivers down his spine and made him scared for his life. Dipper shook off the terrifying feeling and got new clothes and his extra vest, grabbing his book and heading to McGucket's place. Over the years, quite a lot of his hair grew back and he was back doing research but only Dipper and Mabel knew so he depended on him a lot.

The teen walked deep into the old man's junk yard and looked around before going behind a piece of cloth that was hanging. Old man McGucket was going through papers with his glasses that he repaired. All around him was an office with handmade computers and such. He had gained his intelligence back yet he didn't know when people where sneaking behind him. "Fiddleford?" Dipper asked when behind the old man. "Wah!" The old man jumped and looked at him startled. "Oh, it's just you, Dipper… Is there something you needed?" Dipper nodded and went through his journal, across from the other. "Yeah… It's about Bill Cipher." Fiddleford's eyes widened at the name and he stood up. "The dream demon?"

He nodded and showed him his journal. "Yeah, him. Mabel made a deal with him and I'm trying to stop it." The old man looked in thought before sitting back down. "There's nothing you can do it break a deal. Unless… You actually make a deal with the demon itself to prevent anything bad to happen. But then, you're at Bill Cipher's mercy." Dipper looked down and thought hard. "Are you sure? There must be another way." Fiddleford shook his head. "I can't think of another way, Dipper. Either you see how Shooting Star does or you make a deal." He sighed in frustration and lifted his hat, running a hand through his hair. "Alright… I'll catch you later, McGucket." The old man nodded and he walked out of the insane man's office. Little did he know, the real Fiddleford was in the mindscape trying to tell him the only way to stop Bill Cipher.

"You're mine, Dipper Pines."


End file.
